Preparation of product containing sodium acid cyanamide



Nov. 10, 1953v R. A. VINGEE ErAL PREPARATION OF' PRODUCT CONTAINING SODIUM ACID CYANAMIDE Filed Nov. 23, 1949 lNvENroRs fam/MON@ 4. l//A/Gff, L off/ s L 5A/70, df?,

' BY @Q qnm L HMM-f ATTORNEY Patented Nov. 10, 1953 PREPARATION F PRODUCT CONTAINING SODIUM ACID CYANAMIDE Raymond A. Vingee, Stamford, and Louis L. Lento, Jr., Springdale, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application November 23, 1949, Serial No. 129,165 Claims. (Cl. '7l- 2.2)

The present invention relates to the preparation of a defoliant containing an alkali metal acid V cyanamide.

.It is an object of the invention to prepare such a defoliant in greater yield and at considerably less cost than has been possible in the past. A further object is to react calcium cyanamide and. an alkali metal hydroxide in an aqueous Imedium with small loss of cyanamide nitrogen and with high conversion of calcium cyanamide to alkali metal acid cyanamide. A still further object is to dry the aqueous reaction mass under conditions that result in minimum decomposition. Additional objects will be apparent from the discussion hereinafter. l In arid regions, which are comparatively dewless, the alkali metal acid defoliants are considerably superior to calcium cyanamide. However, their application prior to the present invention was inhibited by their high cost, there being no means known to prepare them commercially in a price range comparable to that of -calcium cyanamide. Such an economic means is disclosed in the present invention.

The iigure of the accompanying drawing shows the effect of various temperatures and reaction times on the yield of\sodium acid cyanamide.

The probable reactionmechanism in converting. calcium cyanamide vto an alkali metal acid cyanamide can be written rather simply:

The ease with which this reaction can be carried out is, however, more apparent than real. Actually, it is very diicult to obtain good yields of alkali metal acid cyanamide by the above reaction. The main difficulty is the decomposition resulting from the evaporation of the aqueous medium. In these side reactions, cyanamide nitrogen tends to be converted to urea, ammonia, and the like. As a matter of fact, in investigating conditions necessary to provide a maximum yield of alkali metal acid cyanamide while simultaneously reducing the decomposition of cyanamide nitrogen to a minimum, it was found that several factors were critical, such as the amount of water in the reaction mass, the temperature of reaction, the alkali metal compound chosen, and the reaction time.

The following example illustrates without limiting the invention.

Eample Into the feed-in of a pug mill of 75 lbs. per

hour capacity is continuously charged at the rate of 50 lbs. per hour a mixture consisting of.9 lbs.

ofv lime nitrogen, 2 lbs. of water, 3.1bs. of sodium hydroxide, and 1A; lb. of a wetting agent of the type described in more detail below. The method of preparing and feeding the charge is not critical. Solids may be added to liquid, or vice versa. The pug mill is heated by means of a steam jacket or the like so that a temperature of 100 C. is maintained. Using the above ratio of feedto-capacity, the residence time of 11/2 hours -is obtained, and the product leaving the mill is found to contain about 25% sodium acid cyan,-v amide, and to be nearly dry. The water content is 1-1.5%. The product so obtained .may be ground and applied asa defoliant without further treatment. If alengthy storage period is contemplated, however, it is preferably dried further to a water content of 0.5-0.'7% in an auxiliaryv drier.

It is a remarkable feature of the invention that at least four elements of theV reaction are critical, namely: y

l. The time of reaction must be at least 1 hour. 2. The temperature of the reaction must lie within the range -110 C.

g V3. The alkali metal reactant must be a hydroxide.

, V4. The amount of water used per mol of calpium cyanamide must be at least l mol butA not lmore than 2 mols. For best operation, no more 'than 1.5 mols of water per mol of calcium cyanamide is preferred.

ywetting"agent While it is not necessary to use a wetting agent in the process, it has been found that the addition of a small amount-even as low as one part in 500 parts of reactants-reduces the consistency of the reaction mass to a remarkable degree and permits the use of a minimum amount of water and a minimum amount of power consumption in stirring the mass. The result is a shorter reaction period with an overall gain in the grade of sodium acid cyanamide. Thus, the use of a wetting agent serves two unrelated ends, namely, it improves the grade of material while simultaneously produces a product that can be used as vsuch in arid areas. The wetting agent used should be stable to calcium ions. Among such wetting agents are the various sulfonated wetting agents such as Turkey red oil, the wetting agent known as nytron, made by reacting long-chain olefns with nytrosyl chloride and preparing an adduct with sodium sulte. Still other suitable wetting agents are the alkylated aryl sulfonates, such as naccanol, aerosol OS, and the like.

Of course, the wetting agents chosen must be stable within the temperature range 90-110 C.

range) begins to reach the optimum only after 10 a reaction period of about 1 to 11A hou1's ,andia maximum only after 11/2 hours. It Willbeseenf, therefore, that the rate of `feed ,in tc, the apparatus must be controlled to givea residenotime A (or reaction time) of at leaSlQl` 130111 -to 1V2hours. 15;

Temperature of reaction From Fig. 1 it will be noted-that reaction.temel peratures of 60 and 120 C. respectivelyfail .to

provide the desired grademf sodium acid cyan- 2 amide. The temperaturarange 90%110" C. is critica-hand deviations therefrom -Will 4result vin a norrgon'irnercialfgrade-fofl defoliant. Y

Itr-has' been .found .-.thatonly the alkali -metal 25 hydroxidesacan be used .-in :this process. Thisl group -includesisodium hydroxide; `potassium .hy-Y droxidefand the.l-ike.= Potassium hydroxidegives a slightly;bettenY product than sodium-hydroxide, 30, a calumstame wetting-@gnamplsgmlmL but 'owing'- gtoxthe low- .cost f of the latter, sodium hydroxide isrpreferred.` Using the. same critical conditions, :when the process, is :run With -a `nonhydroxide1 material, for Yexample `sodium carbonate'th'e yield .ofsodium acidf cyanamidel dropped 35,

to2-:1.12%. A

Water'v While T it ',is; ,necessary to', use an Y amount, of Wateigsuflioient .to insure an ionic ,double y,olecom,

position reaction, it is 'also important to keep 'loy thefvolumeowaterlow in order Yto,av,oida long evaporatng.. zperiod `which tends to, decompose the cyanamide ion. It will be readily` appreciated that the, amount ,ot water suitahlejrom the. commerciahproduction of s'o di1.1m acidP tcyariamid'e is 4.5-

critical Iand falls Within-a lnarrovi..range .Obvif ouslyat least..a stoichiometricquantity of Water should be present. However, beyond this amount that quantity, present should bereduced as much as,.possibl.el.tol avoid excessive drying tirnesny It 50 has ,been found V`that noA mQre than 2 mclsof water per moly .or contained calcium cyanamideA canbe used if a commercial grade of defoliant ,is ,to be obtained, and it is greatly preferred to use even less, namely about:1.01.5 vmols of water. 55

calcium ncya-namide known as ulimeuiitrogen is 50 quite satisfactory for use in practicing this invention. When using lime nitrogen the stoichiometric quantity of calcium cyanamide should be calculated on the basis of the amount contained in the lime nitrogen. This will generally fall within .the .lange 56- 69% ,In the.. interests of A 'economy the amount of alkali @metal hydroxide or cyanamide should be approximately theoretical, though a commercial grade of defoliant can be obtained when the amount of hydroxide is only 80%"ofatheoretical- Reference-ais made to application Serial No. 22,1,53,2,i `1led,April,17, Y1951, which is a continuationfin-.partqoL- Serial No. 129,166, filed by one ofgthiinstantfjointrapplicants with another.

Wh-ilegthe--nyentivon has been described with particular; reference to specific embodiments, it is to-be understood that-it is not to be limited theretofbutgisgto be construed broadly and restricted 0 solely by the scope of thefappended claims.

1. ,The method Qfrreparina a nrodilsicontein; ing an alkali metal acid cyanamideandcalcium hydroxide..comprisinabeatins .a mixture. of, cal# ciumoyanamide. .Weten .and anA alkali :metal hydroxide. respective Vcil Ciurniwafe 1fr'alkali metal hydroxide mol ratio'i about ,1 i-,2 1;,1, 'et e temperature of, ,90" +1l0j-C for,M at, least one hour.

2- "The method. @coordinato claim.; 'mlrvhh.

3. zThe method according. tecla-imi in yvhich calcium cyanamiden .is Y. present as lime-.nitrogem 4. The` method.. cfT ,preparingI ,a .,defoliant con;V taining-Sodium acideeyanamide andaceleum his droxide which comprises rn,ix ing, yvater,lime ni, trogen Yand sodiurmhydroxide in A.the l .ygiroportions ofclaim i to.; `forrxrn a reaction,.maS,S.;.f advancing said mass throusha reactiomzone.mantainedat approximately, 90?.-110" .C. during@J reactionpq-f. riodA of atleast ,1 houmwith ,appropriatejagitation to" driveoi eXCES--zWater and trecoveriing. a sub.-r stantially: dry. productpat the.,terrx iir iu s,;of said zone.-l Y Y 5. The method according.to. .claim 4 in which :a Calciumestable. wettingfTagent ist pleisrtritfV mathe reactionmass.A`

RAYMOND: A. LOUIS. L. :LENTOLJR-rf.

References Cited. `in. the ile A gf, .thS- @allient UNI'IED .STATESfTENTS 

1. THE METHOD OF PREPARING A PRODUCT CONTAINING AN ALKALI METAL ACID CYANAMIDE AND CALCIUM HYDROXIDE COMPRISING HEATING A MIXTURE OF CALCIUM CYANAMIDE, WATER, AND AN ALKALI METAL HYDROXIDE IN THE RESPECTIVE CALCIUM:WATER:ALKALI METAL HYDROXIDE MOL RATIO OF ABOUT 1:1-2:1, AT A TEMPERATURE OF 90*-110* C. FOR AT LEAST ONE HOUR. 